As an avid user of acrylics, I'm always interested in product claims.
One manufacturer claims to have the highest molecular weight continuous processed acrylic sheet. Having this property claims to make the plastic easier to work with among other things. What does *high molecular weight* mean? I guess more PMMA molecules than additives? How does this give it these superior properties?
Below is the website I stumbled upon while searching for something related.
spelling correction in title...
Atoms and molecules, even though they are very small, still have a mass (weight) associated with them. A cabon atom for instance, weighs about 1.99 x 10^-23 grams. This manufacturer is simply saying that their PMMA molecules weigh more than anyone elses.
If you were to take same-size samples of this material and another competitive product, and if both samples had additives at the same level (say 1%), the high molecular weight samples would actually have a lower molecules-to-additives ratio since there are fewer PMMA molecules in that sample.
Higher molecular weight in general will make stronger polymers. It's the difference between parafin wax and a piece of polyethylene (such as is used in a milk jug) and the ultrahigh molecular weight polyethylene used in Spectra ropes, which on a per-weight basis are stronger than steel. It is not however always the case that higher molecular weight means higher strength. It has to be used correctly. I can get into more details if you wish, but I think this might be enough information to answer you for now.
John
Doubt if molecular weight is the whole story. All sheets that I know of have additives including comonomers and stabilizers. High molecular weight beyond a certain point is not significant unless the polymer is oriented. Some acrylic sheets are extruded from finished polymer and some are cast from monomer. Major manufacturers such as Lucite can specify an acrylic sheet that best meets your needs. Frank
This is where I'm confused. How can a molecule of substance A be heavier than someone elses substance A molecule?
I guess I need to look a the parafin wax molecule vs. PE. The molecule is heavier because carbon chain is longer? Thanks for your explanation, John
Sorry, I should have explained this yesterday. Most chemicals have a well defined structure. Water is H2O and so all the molecules weigh the same. Polymers, such as PMMA, do not have as well defined of a structure. The molecules are made by reacting MMA monomers together to form long chains. All of the chains are not of the same length, and hence the weight will vary as well. (In fact, it is not possible for any manufacturer to make all of there PMMA chains all of the same length. There is always a distribution of sizes to it.)
John
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